Flow restricting device



Nov. 16, 1954 J. R. PROSEK ETAL 2,694,296

FLOW RESTRICTING DEVICE Filed Oct. 15, 1951 2 Sheets-Sheet l FIFE/6517A7' 101V 52 29 ,30 37 REFR/EERATION ro VAPORA roR 7'0 M4PORATOR 7'0CAPILLARY 17 2 enzons:

4/5677, If 1 70821? a/s e vfi 'alazzz' United States Patent FLOWRESTRICTIN G DEVICE John R. Prosek and Joseph A. Galazzi, Evansville,Ind.,

assignors to international Harvester Company, a corporation of NewJersey Application October 15, 1951, Serial No. 251,400 6 Claims. (Cl.62-115) This invention relates to flow restricting devices generally,but more particularly to a refrigerant flow restricting mechanismadapted for use in a refrigeration system wherein defrosting of thecooling unit is accomplished by reversing direction of flow ofrefrigerant through portions of the refrigerating apparatus.

ln the modern household refrigerator using thecompressor-condenser-evaporator-type refrigerating system, periodicdefrosting of the evaporator cooling element, for the purpose ofremoving accumulations of frost-like condensate thereon, may beaccomplished by any one of several different methods. One method,however, that has found some favor in the industry involves reversingthe direction of flow of refrigerant through a portion of the apparatuswhereby the hot compressed refrigerant gases from the compressor aredirected into the evaporator cooling unit instead of into the condenser.

1n arrangements of this character the heat of the compressed refrigerantis employed to raise the temperature of the evaporator surfacessufliciently to effect a melting of any ice or frost accumulatedthereon, and when the elevation of this temperature is accomplished withconsiderable rapidity there is no appreciable change in the temperatureof the food products stored in the refrigerator. If, however, thetemperature of the compressed refrigerant is not suflicient to rapidlyeffect a melting of the accumulated frost, and such reverse flowoperation has to be continued to for an appreciable length of time,there is a danger that the temperatures in the food storage compartmentswill likewise be raised sufliciently to cause damage to any food storedtherewithin.

In the past, defrosting systems of this character have not been entirelysatisfactory primarily because the length of time required to effectdefrosting of the evaporator was so great that a noticeable rise intemperature in the food storage compartments usually accompanied suchreverse flow operation with the consequent prospect of food damageunless closely supervised. The basic reason for such slow andunsatisfactory operation was found to be primarily the result ofattempting to operate the refrigeration system on the reverse cycle withthe same degree of refrigerant flow restriction as that employed on therefrigeration cycle. It was found, however, that on the reverse ordefrost cycle, the desirable pressure drop from the evaporator unitthrough the restricting device to the condenser unit is somewhat lessthan that ordinarily required for satisfactory operation on therefrigeration cycle; hence when the same degree of restriction isemployed on both cycles unsatisfactory operation can be expected on atleast one of the cycles. Since the refrigeration system is mostfrequently balanced for ideal operation on the refrigeration cycle, andsince no suitable means has heretofore been developed to compensate foror to accommodate such desired variation in fiow restriction, it willreadily be understood why the operation of such a system on the reverseor defrost cycle will not be entirely satisfactory.

In the conventional refrigeration system, an expansion valve or acapillary tube is generally used to reduce pressure and to meter theflow of refrigerant between the condenser and evaporator; but when thedirection of flow of refrigerant therein is frequently or periodicallyreversed, as for defrosting purposes, the fixed and inflexiblecharacteristics of these devices limit their adaptability andusefulness. The expansion valve, for instance, is essentially auni-directional flow device, while the capillary tube restrictor, withits substantially identical flow restricting characteristics in bothdirections, cannot be balanced for effective reverse flow operation and,at the same time, provide satisfactory operation during therefrigeration cycle. When properly balanced for normal operation thecapillary tube otters so much restriction to flow that in the reversedirection the refrigerant entering the evaporator remains largely in theevaporator. As a consequence, the passage or refrigerant is so slow thatheating of the food storage compartments frequently occurs beforedefrosting is accomplished. Neither of these well known prior artrestricting devices, therefore, has ever been entirely satisfactory foroperation in a refrigeration system wherein refrigerant flow isoccasionally reversed, as for defrosting purposes, and flow restrictingcharacteristics differing from those of the refrigeration cycle must beprovided. Furthermore, no other simple highly effective means capable ofsatisfactorily performing under such varying flow conditions hasheretofore been proposed, hence it is readily understandable whydefrosting systems using the reverse refrigerant flow principle have notbeen more universally accepted. The present invention, however, doesprovide the desired variation in flow restriction when direction ofrefrigerant flow through the circuit is reversed, hence it effectivelyovercomes the difficulties heretofore encounteredin a refrigeratingsystem when such system employed a reverse cycle operation fordefrosting purposes.

It is a principal object of this invention, therefore, to provide in arefrigerating system refrigerant flow restricting means which offers apredetermined restriction to the flow of refrigerant therethrough in onedirection and a different restriction to flow therethrough in theopposite direction.

Another object is to provide an auxiliary flow restrictor for use in arefrigerating system which is adaptable for increasing the restrictionto refrigerant flow in one direction through the system.

A further object is to provide an improved refrigerating system whereinthe evaporator cooling element is defrosted by reversing the directionof flow of refrigerant therethrough.

A still further object is to provide a refrigerating system having areversing valve therein whereby the direction of flow of refrigerantthrough portions of the circuit may be reversed for the purpose ofdefrosting the evaporator cooling element of the system.

A yet still further object is to provide an auxiliary flow restrictordevice adaptable for use with a capillary tube restrictor in arefrigerating system for increasing the restriction to refrigerantflowing in one direction only through the syste Another important objectis to provide a simple, rugged, non-adjustable and inexpensive flowrestrictor device having no movable parts and arranged to offer agreater resistance to flow of refrigerant therethrough in one directionthan in the opposite direction, and which is adaptable for use in arefrigerating system that may be operated on reverse cycle fordefrosting purposes.

A further important object is to provide a refrigerant flow restrictingdevice having a chamber and choke means therewithin for increasingturbulence and the resistance to flow when refrigerant flowstherethrough in one direction.

The foregoing and other objects and features of the invention willbecome apparent as the disclosure is more fully made in the followingdetailed description of a preferred embodiment of the invention asillustrated in the accompanying sheets of drawings, in which:

Fig. 1 is a schematic diagram of a refrigerating system embodying therestrictor device of the present invention, the refrigerating apparatusbeing shown in operating position for producing refrigeration of theevaporator.

Fig. 2 is an enlarged sectional view of a preferred form of theauxiliary restrictor device of the present invention as employed in therefrigerating system during the refrigeration cycle.

Fig. 3 is a View similar to Fig. 1 but with the refrigerating apparatusshown in operating position for producing defrosting of the evaporator.

Fig. 4 is similar to Fig. 2 but shows the auxiliary restrictor device asit is employed in the refrigeration system during defrosting of theevaporator.

Figs. and 6 are enlarged sectional views showing modified forms orconstructions of the proposed auxiliary restrictor device.

By reference to the drawings it will be noted the refrigerating systemselected for schematic illustration is of the conventionalcompressor-condenser-evaporatortype wherein the direction of flow ofrefrigerant through the evaporator cooling-unit may be reversed, asindicated by the directional arrows in Figs; 1 and 3, in order to effectthe defrosting thereof. In Fig. l, for instance, the direction of flowof refrigerant through the system, as indicated by the arrows, is shownas normal or that which will produce refrigeration of the cooling unit,while in Fig, 3 the direction of refrigerant flow through portions ofthe system is shown, as indicated by the arrows, as reversed withrespect to that of Fig. 1, and the system as so operated will producedefrosting of the cooling unit.

In a refrigerating system of this character, the discharge outlet of aconventional motor-compressor unit 10 is connectedby a conduit 11 to anopening 12 in a reversing valve device 13, an opposite outlet 14 ofwhich connects by a conduit 15 to the inlet of a condenser 16 while theoutlet of said condenser may, if desired, be connected by a conduit 17to a drier unit 18, the opposite side of which connects by a conduit 19to the inlet of a capillary restrictor tube 20. The outlet of saidcapillary, in accordance with the teachings of the present invention,may connect by conduit 21 to one side of an auxiliary restrictor device,indicated generally by the numeral 22, while the opposite side or outletthereof is connected by conduit 23 to the inlet of an evaporator coolingunit 24. The outlet of said evaporator connects by a conduit 25' to anopening 26, of the reversing valve 13, and a corresponding oppositeoutlet passage 27 of said valve connects by conduit 28 to the suctioninlet of said motor-compressor unit. It will be understood, of course,that refrigerant will be circulated within the apparatus for purposes ofeffecting refrigeration.

The individual components or units of the system, with the exception ofthe auxiliary restrictor 22, are generally conventional, and, sincetheir specific use and application in a refrigerating system are wellunderstood in the art, it is believed further description of thestructural details thereof, and of the conventional control devicesgenerally associated therewith, is unnecessary.

The reversing valve 13 is, preferably, of the conventional 4-way type,such for instance as is described and illustrated-in the Walfert Patent2,342,566, dated February 22, 1944, having dual inlets and outlets andcanals or passageways therewithin arranged so that refrigerant incomingfrom the compressor may be directed, either, to the opening 14 leadingto the condenser or to the opening 26 that is connected by a conduitwith the evaporator. It should be understood, of course, that whenrefrigerant incoming from the compressor through opening 12 is directed,by way of opening 26, to the evaporator, instead of through opening 14to the condenser, the discharge from the condenser will be directed fromthe valve opening 14 across to the opening 27 that connects said valve,by way of conduit 28, to the suction side of the compressor, therebyeffecting a reversal of refrigerant flow through portions of the system.Since valves of this character are generally old and well known in theart as heretofore indicated, and since the specific valve mechanismemployed is not pertinent to the operation of the instant invention, thedetails thereof have not been shown with any great degree ofparticularity. Likewise, means for operating said valve have beenomitted because it is immaterial whether manual, senili-automatic orautomatic operation is employed therewit In one preferred embodiment, asillustrated in the sectional views of Fig. 2 and 4, the proposedauxiliary restrictor device 22 is depicted as fashioned with a tubularouter member 29 having the opposite ends thereof swaged or otherwisedrawn to provide reduced section portions indicated, respectively, at 30and 31. Intermediate the reduced ends of said outer tubular member,there is provided a fluid choke device fashioned, preferably, as alongitudinally extending core-like circular plug member 32 shaped toconform with the interior surface of said tubular member. The oppositeends of said plug are trimmed so as to present substantially flat endwall surfaces 33 and 34, respectively, that are normally disposed withrespect to the longitudinal axis thereof, while a cone-shaped or taperedpassageway 35 extending through the center of the plug connects a smallopening 36, in the end wall 34, with an enlarged opening 37 in theopposite end wall 33. The end walls, 33 and 34, are inwardly spaced fromthe respective reduced end portions of said outer tubular member so asto provide expansion or turbulence chambers 38 and 39. If desired, saidplug member may be fashioned as an integral portion of the tubular outermember but, preferably, it is separately fabricated and then positionedin'said tubular member in a press-fit relationship so that oncepositioned therewithin it will remain fixedly disposed indefinitely. Ifdesired, of course, the tubular member may be long enough to positiontwo or more such plug-like members at spaced intervals therewithin forthe purpose of increasing resistance to refrigerant flow therethrough.

In operation, the proposed auxiliary restrictor functions to restrictthe flow of refrigerant between the capillary tube and theevaporatorinlet and thus aids or supplements the restricting action ofsaid capillary when the refrigerating system operates on therefrigeration cycle. When the refrigerant from the capillary firstenters said auxiliary restrictor, it passes into the chamber 39 where itmay expand and bombard or impinge against the barrier provided by theend wall 34 of the plug member 32. As a result of such action, aturbulence is set up within said chamber which operates to increase theentrance loss and thus permits only a small or limited portion of therefrigerant to pass, by way of the small opening 36, passageway 35, andthe enlarged opening 37, into the chamber 38 at the opposite end of saidrestrictor. The turbulence thus set up will continue, so long asrefrigerant flows thereinto, to retard or restrict the movement of saidrefrigerant through said restrictor, thereby aiding or supplementing thecapillary tube in restricting refrigerant flow between the condenser andevaporator units. On the other hand, when the system is operating on thedefrost cycle the direction of refrigerant flow is from the evaporator24, through the auxiliary restrictor 22, to the capillary tube 20, inwhich case refrigerant enters the restrictor through conduit 23 andflows immediately into the expansion or turbulence chamber 38. Since theend wall barrier 33 provides very limited restriction, and since theopening 37 is enlarged, there is very limited opportunity for setting upany appreciable turbulence to restrict flow therethrough; hencerefrigerant flows easily into and along the gradually taperingpassageway 35 and discharges through the opening 36 into chamber 39 fromwhere it passes by way of conduit 21 into the capillary tube. It willreadily be appreciated that the flow of refrigerant through theauxiliary restrictor in this direction is substantially free flowing anduninhibited; consequently, substantially no turbulence is producedtherewithin and restriction to flow of refrigerant therethrough isminimized. Under these conditions the auxiliary restrictor does notappreciably add to or supplement the capillary tube in providing arestriction to refrigerant flow between different portions of therefrigerating system.

In Figs. 5 and 6, two modifications of the proposed restrictor devicedepict structures that differ slightly in construction from thepreferred embodiment heretofore described, but which function insubstantially identical fashion to produce the same desirable result.Direction arrows on these views indicate the direction of refrigerantflow therethrough during the respective refrigeration and defrostingcycles. In Fig. 5 the restrictor shown includes a tubular outer member40 having reduced end portions 41 and 42, and a choke-like plug member43 positioned therewithin between the chambers 44 and 45. The plug 43 isshaped, preferably, to conform substantially with the interior surfaceof said outer member and is positioned therewithin in a press-fitrelationship. Opposite ends of said plug are fashioned to presentsurfaces 46 and 47 normally disposed with respect to the longitudinalaxis thereof. A bore or passageway 48 that diminishes in cross-sectionaldimension throughout its length extends from end to end through thecenter of the plug. A passageway such as indicated may be fashioned froma series of successively graduated, axially aligned adjacent bores 49,50 and 51 that are arranged to cooperate and form steps or setbackledges 52 and 53 disposed at spaced intervals along the walls of saidbores.

The restrictor depicted in rig. 6 includes a tubular outer member 54having reduced end portions 55 and 56, and a choke plug member 57positioned therewithin between the chambers 58 and 59. The plug 57 isshaped, preferably, to conform substantially with the interior surfaceof said outer member and is positioned therewithin in a press-fitrelationship. One end of said plug is fashioned to present a flat endsurface 60 that is normal to the longitudinal axis thereof, while theopposite end is fashioned with a longitudinal offset 61 that joinsaxially spaced flat end surfaces 62 and 63 likewise normally disposedwith respect to said longitudinal axis, and a tapered or cone-shapedbore or passageway 64 that extends from end-to-end therethrough.

In operation, the restrictors of Figs. 5 and 6 function in much the samefashion as previously described in connection with the embodimentillustrated in Figs. 14. During the refrigeration cycle, in therestrictor depicted in Fig. 5, refrigerant flows from the capillary byway of conduit 21, into the chamber 45 where it bombards and impingesfirst against the barrier wall 47 and then, successively, against theledges 52 and 53 within the passageway 48. Since entrance losses areknown to rapidly multiply, as a result of sharp bends or rapid changesin direction of the flow of a fluid, it will be appreciated that theledges 52 and 53 operate to supplement the action of the wall barrier 47in setting up a restricting turbulence that tends to restrict the flowof refrigerant from the capillary 20, through the tapered passageway 48and chamber 44, into the evaporator 24. On the defrost cycle however,the flow through the restrictor being in the reverse direction, therefrigerant will flow more freely because only the one wall barrier 46is disposed in the path thereof to create or set up a turbulence. As aconsequence, substantially less turbulence will be created and noappreciable or seriously objectionable restriction to flow through therestrictor in this direction will be encountered. Likwise, in Fig. 6,during the refrigeration cycle, the offset surfaces 62 and 63, of theend wall barrier, operate to restrict flow and produce turbulence whenrefrigerant impinges thereagainst, but during the defrost cycle, whenrefrigerant flows through the restrictor in the reverse direction, noappreciable resistance or restriction is encountered, thus therestriction to flow therethrough is minimized.

From the foregoing, it will be readily apparent that the proposedrefrigerant flow restrictor represents a new,

novel and highly etfective device that will greatly im prove theoperation of a refrigeration system employing the reverse flow principlefor defrosting the cooling unit thereof. Furthermore, the proposeddevice is simple, inexpensive, and contains no movable parts or elementsthat might readily wear, deteriorate or get out of adjustment as aresult of normal use. In addition, the proposed restrictor is readilyadaptable to any conventional refrigeration system and requires only aminimum of modification or alteration to permit its installation in therefrigeration circuit.

Although only a preferred form of the invention, and

several structural modifications thereof, has been illustrated anddescribed in detail, it will be apparent to those skilled in the artthat various other modifications may be made therein without departingfrom the spirit of the invention or from the scope of the appendedclaims.

What is claimed is:

1. A flow-restricting device for restricting flow of refrigerant througha refrigerating system comprising: a longitudinal member having acentral bore therethrough and adapted to have one end thereof connectedto one portion and the other end connected to another portion of arefrigerating system, fluid-restricting means within said member, saidmeans including a choke member disposed in spaced relation to the endsof said longitudinal member and arranged so as to provide a chamberbetween each end of said choke member and the respective proximate endof said longitudinal member, said choke member having one end thereofsubstantially flat and normally disposed with respect to thelongitudinal axes thereof while the opposite end of said member isfashioned with an axially extending oifset that forms said end portioninto two axially spaced end face surfaces normally disposed with respectto the longitudinal axes, and having said choke member further providedwith a gradually tapering bore extending longitudinally therethrough andcommunicating with the chambers at opposite ends thereof.

2-. In refrigerating apparatus, the combination of a compressor, acondenser, an evaporator, a flow-restricting tube, a flow-reversingvalve, tubing connecting said condenser, flow-restricting tube, andevaporator in series, additional tubing connecting said flow-reversingvalve with the compressor, condenser, and evaporator, in operatingrelationship whereby said reversing valve functions to direct the flowof refrigerant from the compressor selectively either through thecondenser and thereafter through the flowrestrieting tube and theevaporator in one direction or through the evaporator in the oppositedirection and thereafter through the flow-restricting tube and thecondenser, additional flow-restricting means characterizedby havinggreater restriction to flow when refrigerant flows therethrough from thecondenser to the evaporator than when refrigerant flows therethroughfrom the evaporator to the condenser, and tubing connecting the saidresatricting means in series with the said flow-restricting tu e.

3. In refrigerating apparatus, the combination of a compressor, aflow-reversing valve, a condenser, a flowrestricting tube, anevaporator, tubing connecting said condenser, flow-restricting tube, andevaporator in series, additional tubing connecting said flow-reversingvalve with said compressor, condenser, and evaporator in operatingrelationship whereby said reversing valve functions to direct the flowof refrigerant from the compressor selectively either through thecondenser and thereafter through the flow-restricting tube and theevaporator in one direction or through the evaporator in the oppositedirection and thereafter through the flow-restricting tube and thecondenser, a flow-restricting device, and tubing connecting the saidflow-restricting device in series in the tubing that connects the saidflowrestricting tube with said evaporator, said flow-restricting devicebeing additional to the flow-restricting tube and constituting togetherwith said flowrestricting tube a flow-restricting means characterized byhaving a high restriction to the flow of refrigerant when the directionof flow is from the condenser through the flow-restricting tube andflow-restricting device to the evaporator and a low restriction to theflow of refrigerant when the direction of flow is from the evaporatorthrough the flow-restricting' device and flow-restricting tube to thecondenser.

4. In refrigerating apparatus, the combination of a compressor, acondenser, an evaporator, a capillary tube fiow restrictor wherein therestriction to flow is the same in either direction for a refrigerantflowing therethrough under identical conditions of temperature andpressure in both directions, a flow-reversing valve, tubing connectingsaid condenser, capillary tube flow restrictor, and evaporator inseries, additional tubing connecting said flow-reversing valve with saidcompressor, condenser, and evaporator, in operating relationship wherebysaid reversing valve functions to direct the flow of refrigerant fromthe compressor selectively either through the condenser and thereafterthrough the capillary tube flow restrictor to the evaporator in onedirection or through the evaporator in the opposite direction andthereafter through the capillary tube flow restrictor to the condenser,additional floW-restricting means connected in series between thecondenser and evaporator, said additional flow-restricting meansincluding a flow-restricting device characterized by a relatively largepressure drop when the fiow of refrigerant therethrough is from thecondenser through the capillary tube flow restrictor and said additionalflow-restricting device to the evaporator and a relatively smallpressure drop when the flow of refrigerant is in the reverse direction.

5. In refrigerating apparatus, the combination of a compressor, acondenser, an evaporator, flow-restricting means in which therestriction to the flow of a refrigerant therethrough is a function ofdirection of flow whereby the restriction to flow through said means inone direction and at any given temperature and pressure is greater thanthe restriction to flow therethrough in the opposite direction at thesame temperature and pressure, a flow-reversing valve, tubing connectingsaid condenser, flow-restricting means, and evaporator in series,additional tubing connecting said flow-reversing valve with saidcompressor, condenser, and evaporator, in

operating. relationship whereby said reversing valve functions to directthe flow of refrigerant from the compressor selectively either throughthe condenser and thereafter through the. flow-restricting means and theevaporator in one direction or through the evaporator in the oppositedirection and thereafter through the flowrestricting means and thecondenser.

6. The combination recited in claim 5, and further characterized byhavingrsaid flow-restricting means include a length of small diameteredcapillary tubing connected to a tubular member having a choke therein,and having the choke positioned so that the flow-restricting meansoffers the greatest restriction to the flow of a refrigeranttherethrough when the direction of flow is from the capillary tubeportion thereof to and through the choke portion to the evaporator.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,704,177 Davenport Mar. 5, 1929 2,456,626 Dahnke Dec. 21,1948 2,589,384 Hopkins Mar. 18, 1952

